1. Field of the Invention
This invention relates to a solar-hydrocarbon fueled combined cycle power generating plant.
2. Description of the Related Art
The basic concept for this invention was presented in a paper entitled "Solar Central Receiver Hybrid--A Cost Effective Future Power Alternative", published in Journal of Energy, Volume 1, Number 1, January-February 1981. A Solar Central Receiver (SCR) hybrid plant conceptual design was provided utilizing molten salt (60% NaNO3, 40% KNO3 by weight) as a heat transfer and thermal storage medium. Solar energy is utilized with fossil fuels (coal, oil or gas) in various plant configurations. The hybrid plant described in the paper was developed for the Arizona Public Service utility by Martin Marietta Aerospace under a U.S. Department of Energy contract.
The hybrid system flow diagram is presented in the reference paper and includes standard powered plant features such as feedwater heaters, steam generator equipment, a steam turbine-generator, pumps, a solar central receiver, solar collectors, a fossil fueled salt heater, and both cold and hot storage tanks. The system can be operated from solar alone, solar plus storage, storage alone, fossil-fired alone, fossil-fired plus storage, or fossil-fired plus solar. In November 1988 additional studies were published in "Arizona Public Service Utility Solar Central Receiver Study", Report No. DOE/AL/38741-1, Volume 1--Phase 1 Topical Report. The application of a gas turbine waste heat recovery system is included in this latter report.
The power generation stations in these publications utilize relatively large thermal storage systems. These papers do not discuss thermal transient controls which reduce the size and cost of thermal storage systems. The Gas Turbine--Waste Heat to Salt Heater in the Arizona Public Service Utility Solar Central Receiver Study, does not recover the salt heater exhaust energy nor utilize a turbine afterburner configuration. Thermal shielding of the solar central receiver (SCR) to minimize startup times and provide a more efficient transition from solar to fossil operation is not discussed. The designs presented are for molten salt only and do not include provisions for sodium as an optional primary heat transport medium.